1. Field of the Invention
This invention relates to opposed reciprocating piston mechanisms such as internal combustion engines and compressors. The use of shaft eccentrics in combination with pivotally mounted cylinders provides uniflow scavenging through the cylinder with significant reduction in combustion chamber and crankcase sealing requirements.
2. Description of the Prior Art
The primary cause for limited application of the two-stroke cycle engine to commercial use, is related to cylinder air/fuel charge and exhaust problems causing substantial decrease in the actual Mean Effective Pressure (MEP) and the related efficiency of two-stroke engines. It is the cylinder scavenging system which determines the quality of the cylinder charge exchange process.
Efforts to improve scavenging systems have focused primarily on the development of internal crankcase scavenging. These have lead to considerable complexity in crankcase design, the requirement for additional mechanical working components, sealing and lubrication problems in regions in close proximity to the combustion and crankcase chambers, and has added to the cost to manufacture, operate and maintain this type of internal scavenging two-cycle engine.
It is known to the art that the most effective scavenging system is of uniflow design, wherein inlet and exhaust ports are symmetrically positioned at opposite ends of the cylinder to provide a direct flow of charge reactants and exhaust products through the cylinder and wherein the pressure to accomplish such scavenging is generated through the use of an external blower.
As generally disclosed in the prior art, many of the reciprocating piston mechanisms require one or more intermediate power transmissions to transmit power to or from a piston and a drive shaft. In an engine, power is conventionally transmitted from the piston to the connecting rod, then power is transmitted from the connecting rod to the crankshaft which in turn transmits power to a power take-off shaft. The reverse pathway is generally used when the reciprocating piston mechanism is used as a compressor. Use of a connecting rod results in uneven and excessive wear to both the piston and cylinder wall by vectors of force through the connecting rod in directions other than along the centerline axis of the cylinder. When the piston is in any position, other than its top dead center or bottom dead center, transverse, lateral force vectors will be transmitted by the connecting rod causing uneven wear to the piston and cylinder wall.
In recent years various efforts have been made to depart from the conventional engine utilizing reciprocating pistons and stationary cylinders to provide generally improved engine balancing and power output by elimination of connecting rods. Efforts have been made to improve engine balancing and efficiency through development of rotary piston engines such as taught by U.S. Pat. Nos. 3,974,803 and 4,010,675 having rotary movable piston and cylinder piston elements which both rotate within a staionary body forming two variable volume chambers, one of which may serve as a combustion or compression chamber and the other as a precompression chamber. U.S. Pat. No. 3,630,178 teaches a mechanism in which the motion of a working piston is circular and a migrating combustion chamber member forming a pair of combustion chambers. Two additional variable volume chambers are formed between a power block housing and the combustion chamber member for assistance in intake charging and exhaust.
U.S. Pat. No. 3,621,758 teaches a reciprocating piston, pivotally oscillating cylinder internal combustion machine to provide improved aspirating capacity in substantial excess of the displacement of the piston per cycle. In one embodiment, opposed pistons reciprocate in a cylinder mounted to a pivotal platen. Each piston is connected directly to a crankshaft and the end of the piston opposite to the combustion chamber engages a crankcase surface and in cooperation with crankshaft webs provide more complete expansion of working fluid into the crankcase and internal crankcase scavenging. The machine of the '758 patent requires undesirable bearing and frictional surfaces between co-working elements, including the rear end of the pistons and the crankcase housing and between the pivotal platen around the cylinder and the engine block housing. These result in sealing problems and may diminish the useful life of the machine. In addition, the pivotal platen housing the cylinder is of considerable mass and significantly increases the weight of the engine as well as introducing polar inertia considerations.